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Biomedical subjects

M M Burger

Publications and source records attributed to M M Burger.

At least 145 records · Page 8Linked to original sources
PubMed1976

Purification and characterization of two lectins from Caragana arborescens seeds.

A glycoprotein fraction with hemagglutinating activity was purified by affinity chromatography from seeds of the pea tree, Caragana arborescens. Subsequent fractionation resolved two components, which could be separated on a preparative scale using different affinity matrices. The major component binds to N-acetylgalactosamine coupled to Sepharose 4B. It is a glycoprotein with high hemagglutinating activity. It is composed of two types of polypeptides, present in nonstoichiometric amounts, with apparent molecular weights near 30,000. In the native molecule, the subunits are cross-linked by disulfide bonds to form dimers, which in turn appear to be in rapid equilibrium with tetramers. The minor component binds to underivatized Sepharose 4B. It too, is a glycoprotein but has low hemagglutinating activity. It is composed of three types of polypeptides which, although they have apparent molecular weights near 30,000 are distinguished from the subunits of the major hemagglutinin by a number of physical and chemical properties. The native molecule is dimeric, with a mass of 60,000 daltons. The major component has high affinity (K = 0.1 mM) for the haptenic sugar, N-acetylgalactosamine, but will also bind D-galactose. Neither lectin has ABO blood group specificity, nor are they transformed mouse fibroblasts to the same extent.

Acetylgalactosamine↗
PubMed1976

The chromaffin granule surface. Localization of carbohydrate on the cytoplasmic surface of an intracellular organelle.

Intact chromaffin granules from bovine adrenal medulla are shown to have complex carbohydrates on their external (cytoplasmic) surface. This is demonstrated by the facts (1) that granules can be agglutinated by wheat germ agglutinin, and (2) that significant amounts of sialic acid can be removed from the granule surface with neuraminidase. Glycoproteins located in the granule membrane, and not glycolipids, are the molecules that mediate wheat germ agglutinin agglutination. The possible involvement of granule surface carbohydrate in the process of exocytosis is discussed.

Adrenal Medulla↗
PubMed1975

A possible model for cell-cell recognition via surface macromolecules.

Alternative possibilities for the establishment of the proper cell distribution during embryogenesis are summarized at the beginning, followed by an assessment of the examples known so far where cell-cell recognition is known to be mediated via cell surface components. In the second part the species-specific recognition process which occurs during the sorting-out of dissociated sponge cells is analysed since it may serve as a possible model for cell-cell recognition in higher animals. Three possible mechanisms for the establishment of proper cell distribution are considered. These include, first, chemotaxis: secondly, guidance of cell or cell sheet movement by extracellular matrix or by surrounding cells and thirdly, random movement followed by recognition at the final point of destination. Recognition is necessary for both of the two latter processes, i.e. for cell guidance as well as for locking the cells into their final position after random movement. Two basically different recognition mechanisms should be distinguished from each other. On the one hand cells may recognize each other with the help of macromolecules situated in or just outside of the plasmamembrane which fit to each other like enzymes and substrates or antibodies and antigens. On the other hand, cells may exchange information by exchanging cytoplasmatic components via vesicles or gap junctions. The species-specific aggregation of dissociated sponge cells is considered to be a possible model for cell-cell recognition in higher animals. A proteoglycan-like intercellular macromolecule called aggregation factor seems to mediate recognition of a given species of cells in the reaggregation process of dissociated cells. The data available at the present time suggest that a monovalent surface macromolecule (baseplate) may mediate the recognition process probably by recognizing the carbohydrate side chains of the multivalent proteoglycan aggregation factor. A cell-free system was devised to mimic this aggregation process. Addition of aggregation factor to baseplate-coated sepharose beads of approximately the size of the original sponge cells has essentially the same characteristics as the cellular system. Macromolecule-coded surface information for the recognition between cells has not been established during the embryogenesis of higher animals and remains an interesting challenge.

Animals↗
PubMed1975

The characteristics of succinylated con A induced growth inhibition of 3T3 cells in tissue culture.

The growth of untransformed 3T3 fibroblasts can be inhibited by dimeric, non-agglutinating concanavalin A prepared by succinylation (Suc-CON A). This growth inhibition is non-toxic, reversible, and specific for Suc-Con A binding; the cell density at which growth terminates is dependent upon the final cell number and independent of the initial (i.e., plating) density. The part of the cell cycle during which Suc-Con A can exert its growth inhibitory effect appears to be restricted to mitosis and/or early G-1 phase.

Animals↗